Thermostat



Feb. 15, 1938.

E. JUCH HEIM THERMOS'I'IAT Filed March 28, 1936 l Na 0 I .IM I

Hum

Patented Feb. 15, 1938 S PATENT OFFICE THERMOSTAT Erich Juchheim,

llmenau, Germany Application March 28, 1936, Serial No. 71,417

In Germany 6 Claims.

This invention relates to a thermostat in which a nut is mounted on ascrew spindle and carries a contact of wire in a closed glass tube, saidnut and consequently the wire are adjustable in the glass tube byturning the spindle by means of a magnet acting on an armature fixed onthe upper end of the spindle.

The pitch of the spindle thread is so selected, that even if thethermostat is subjected to intensive vibrations it cannot rotate on anddisplace the nut. Further the interior oi the glass tube and theextension of the same can be completely shut off from the outside, owingto the employment of the magnet drive. Such thermostats are absolutelyreliable in service and can be produced as high-grade thermometers evenif the filling is under pressure.

In a known construction of contact thermometers of the type described atravelling nut constructed as an armature or fitted with such anarmature is adjusted by the magnetic field of a magnet rotatablyarranged on the outer side of the extension of the thermometer tube inthat the magnet is rotated, whereby a magnetic rotary field is producedwhich moves the armature.

The travelling nut moves on a stationary spindie; so that this nut orthe armature connected with the same carries out a rotary movementduring the adjusting of the contact of the thermostat and is axiallydisplaced on the spindle. The armature does therefore not remain in thesame plane during the adjusting of the thermometer but moves up or downthe spindle.

This construction is open to the following objectionz- As the armatureto be adjusted by the magnet moves up and down in the widened extensionduring the adjusting of the contactfrom the lowest up to the highestcontact degree, the widened portion must be of comparatively largediameter on its whole length as the armature or the distance between thepoles of the same must be as great as possible to enable the magnet tobe turned through a sufliciently large angle to overcome the resistancescaused by friction during the rotating of the magnet, that is in orderto insure the up or down movement of the armature or of the nutconnected therewith on the spindle.

The permanent magnet arranged on the outer side of the extension of thethermometer tube must either be moved up and down corresponding to themovement of the armature by'means of a screw threaded driveor it must beof disproportionately large size if the contact wire is March 12, 1935displaced in the capillary tube a comparatively long distance, which isusually the case, as the contact point must be made adjustable for thelargest possible range.

Owing to the inconveniences stated such a thermometer or the magneticdrive thereof are very complicated and inconvenient.

According to the invention a nut is guided in a longitudinal guide andsecured against turning. This nut carries a contact wire and is moved upand down by a rotary spindle which is not shiftable in axial directionbut rigidly connected with the armature rotatable by a magnet which whenit is turned rotates the armature and the spindle in one plane causingthe nut to displace on the spindle and adjust the contact wire of thethermostat.

Consequently the widened portion of the thermostat need only besufiiciently large to allow the armature to rotate and the magnet can berelatively small as the armature does not displace relatively thereto.

For effecting the longitudinal guiding of the nut and securing itagainst rotation it is guided in an oval tube forming an extension ofthe thermometer tube and having a widened upper portion accommodatingthe armature. A contact thermometer according to the invention isillustrated by way of example in the accompanying drawing in which:-

Fig. 1 shows the contact thermometer in longitudinal section.

Fig. 2 shows the top part of the thermometer in side elevation;

Fig. 3 is a cross section on IIIIII.

Fig. 4 is a cross section on IV-IV.

Fig. 5 is a cross section on V--V of Fig. 1.

A tube 2 of a thermometer I has an upwardly directed tubular extension 3of larger diameter than the tube 2. This extension has a widened topportion 4 in which a bearing 5, preferably of glass is provided. Asecond. bearing 6 is fitted in the tubular extension 3 near the bottomend thereof.

A screw threaded spindle 9 has pointed ends 1 and 8 engaging in thebearings 5 and 6 respec tively. An armature II! is fixed on the spindle9 in the widened top portion 4 of the extension. A protecting cap ll ofnon-magnetic material, such as brass, artificial resin and the likecovers the widened top portion 4. A permanent magnet l2 with poles N andS adjacent the armature I0 is rotatably mounted on the protecting cap IIand adapted to be turned by means of a milled screw l3 in'the directiona: or 11 around the widened top portion 4. The extension 3 is of ovalcross section and the widened top portion 4 is of round cross section atthe point at which the armature ||l rotates. In the oval extension 3 a.nut I4 is mounted on the screw spindle 9 with indicating line IS. Thecontour of this nut corresponds to the oval shape of the extension 3 sothat this nut cannot turn but must move up and down in this extension 3if the spindle 9 is rotated. A contact wire i6 is fixed on the nut l4and extends downwards therefrom into the thermometer tube 2. At bottomend of the thermometer tube 2 a mercury vessel I1 is arranged and filledwith mercury II. A protecting tube i9 enclosed the thermometer tube 2and the extension 3. In this tube IS a plate 20 is fixed. An adjustingscale 2| is provided at the upper end of this plate and a temperatureindicating scale 22 at the bottom end thereof. A stopper 23 of corkcloses the top end of the protecting tube H. A connecting plate 24 withterminals 25 and 26 is mounted by means of a sleeve 2'! on the top endof the protecting tube I9 and a wire 28 extends from the terminal 26 tothe lower end of the thermometer tube 2 where it passes through the wallof this tube at 29 and is in contact with the mercury it. A second wire30 extends from the terminal 25 downwards along the widened part 3,passes through the wall thereof at 3| and is connected The magnet I2 isthen turned about the cap II. This magnet eiIects the rotation of thearmature ID in the widened top portion of the thermostat and as thescrew spindle 9 is rigidly connected with the armature Ill, it alsorotates, causing the nut I4 to move up or down in the extension 3according to the direction of rotation. By this means the indicatingline IS on the nut i4 is brought opposite the division on the indicatingscale 2| corresponding to the temperature at which the thermostat is tobecome operative. As this nut carries the contact wire it, this wire iscorrespondingly shifted in the thermometer tube 2. The divisions on theadjusting scale 2| correspond with those on the indicating scale 22 andthe position oi. the end 32 of the contact wire I5 relatively to thescale 22 corresponds with the position of the indicating line l5relatively to the scale 2|. Thus, when the line 5 is adjusted to thedivision on the scale 2,1oa,sss

2|, the end 32 will be opposite the corresponding division on the scale22.

When the temperature acting on the thermometer increases, the mercury IIwill risepin the tube 2 until it reaches the end 32 of the contact wireit. The circuit connected up with the terminals 25 and 26 will then beclosed through terminal 26 connected with one pole of the circuit, thewire 28, mercury l8, contact wire I, nut l4, spindle 9, bearing 1, wire30 and terminal 25 connected to the other pole of the circuit.

1. A thermostat, comprising in combination a thermometer tube withmercury filling, an extension on the upper end of said tube, a widenedportion on the upper end of said extension, a bearing in said widenedportion, a second bearing in said extension, a screw spindle mounted insaid bearings, an armature fixed on the upper end of said spindle androtatable in said widened 'portion, a nut on said screw spindle securedagainst rotation in said extension, a magnet rotatable on said widenedportion and adapted to turn said spindle through the intermediary ofsaid armature to shift said nut axially on said spindle. a contact wireextending downwards from said nut into said thermometer tube and adaptedto form an adjustable contact for mercury filling of said thermometer,and a circuit connected up with said mercury and with said contact wirethrough the intermediary of said nut, said spindle and the bearings insaid extension.

2. A thermostat asspecified in claim 1, in which the extension is ofoval cross-section to secure the nut against rotation.

3. A thermostat as specified in claim 1, in

covered by a protecting tube accommodating a' plate with two scales, theupper scale being situated outside the thermometer tube and the lowerscale outside the extension, and the nut having an indicating linecooperating with the divisions of the upper scale to set the contact andthe lower end of the contact wire being adjusted to the graduation ofthe lower scale corresponding to the position of the indicating linerelatively to the upper scale.

ERICH JUCHHEIM.

